Does anyone know how to instruct Compass / Sass to spit out the liquid template tags as they are into the CSS? If I have that, then I have a solid workflow of editing Sass locally, and realizing the changes momentarily after on the shopify shop.

Thanks

EDIT:
By using Hopper's answer below for the liquid tags in Sass, and renaming the Compass output .css file to .css.liquid, I now have an instantaneous workflow for designing a Shopify theme with Compass and Sass!
Here is the code for the Compass callback that goes in the config.rb:

I was trying to do this at one point and got nowhere. It might be possible with a custom SASS extension, or if there is a directive that tells the sass compiler to ignore and output as is, but I didn't find anything that would work.
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John DuffJun 28 '12 at 8:13

I wrote an article describing the methods I used to get Compass and Sass working well with Shopify. This is the same approach of DOMUSNETWORK's answer. I go into a little more detail on file structure.

This worked for me, partially - however I found that the Shopify Theme app a lot of times didn't want to upload my edited .css.liquid file, because apparently it didn't recognize that the file had been edited.

What solved it for me was to use the following code in my config.rb, instead of the code in the question above:

For others who find this answer, I think Quickshot is the tool you are looking for.

You will still need to interpolate for asset urls, but quickshot will automatically recompile your scss and upload the result to shopify in one step. Which also gives you the ability to use @include in your scss files.